Explanation and Rationality Naturalized

Familiar accounts have it that one explains thoughts or actions by showing them to be rational. It is common to find that the standards of rationality presupposed in these accounts are drawn from what would be thought to be aprioristic sources. I advance an argument to show this must be mistaken. But, recent work in epistemology and on rationality takes a less aprioristic approach to such standards. Does the new (psychological or cognitive scientific) realism in accounts of rationality itself significantly improve the prospects for unproblematic forms of rationalizing explanation? Do earlier misgivings about rationalizing explanation ring hollow when the rationality to be attributed is "naturalized"? Answer: while explanation in terms of naturalized rationality would be free of one fatal flaw possessed by explanation in terms of rationality understood in the traditional fashion, it would yet have parallel flaws.